This application is a 35 USC 371 of PCT/EP00/01399 filed Feb. 21, 2000.
The present invention relates to a method of manufacturing outer parts of cross groove constant velocity joints.
With constant velocity joints of this kind, which are described for example in the publication xe2x80x9cUniversal Joint and Driveshaft Design Manual, Advances in Engineering Series No. 7xe2x80x9d of the Society of Automotive Engineers, Inc., the outer part has a cylinder-like internal contour, elongate recesses being made in this. They form ball raceways for the balls arranged in a cage of the inner part. The cylinder-like internal contour of the joint outer part naturally has no undercut. Nevertheless, a separation of outer part and inner part of the constant velocity joint is not immediately possible, since the ball raceways are not axis parallel and furthermore run inclined to one another.
A method of manufacturing joint outer parts of the kind just described is disclosed in patent EP 0 270 538. There, a preliminary workpiece has the shape of a goblet diverging towards the open end, the ball raceways already being pre-formed in its inner side. By means of extrusion drawing of the preliminary workpiece into a cylinder-like opening of an outer die, the preliminary workpiece is so shaped that it finally has a cylinder-shaped internal contour. The necessary force is thereby exercised via an extrusion die which is formed of a plurality of segments movable with respect to one another. These have elevations inclined with respect to one another. There is axially introduced into a hollow chamber located in the extrusion die, before the extrusion of the preliminary workpiece, a spreader which holds the segments in their operative disposition. Upon drawing and shaping of the preliminary workpiece, the elevations of the segments exercise pressure on the inner side of the preliminary workpiece and act in a cold forming manner on the ball raceways inclined with respect to one another.
For removing the extrusion die from the thus worked joint outer part the spreader is first removed from the extrusion die. As a consequence, the segments tilt in the direction of the central axis of the overall arrangement and thus come out of engagement with the ball raceways. In a second step, the segments can then also be removed out of the finished workpiece.
Another method of manufacturing outer parts of constant velocity joints is known from German patent DE 196 37 839, which is however restricted to the manufacture of so-called Rzeppa constant velocity joints. In contrast to the cross groove joint outer parts, with this type of joint the ball raceways run in axial direction. Here, an axial separation of outer and inner parts of the constant velocity joint is prevented in that either the ball raceways and/or the cage guide surface have an axial undercut. With this known method the preliminary workpiece is likewise subjected to cold forming in a working operation. This is effected by means of a wobble extrusion die which is segment-wise differently convexly curved, which is first introduced into the hollow chamber of the preliminary workpiece mounted and fixed in an outer die. Due to the different curvatures of the segments, the wobble extrusion die has rib-like contours on its outer surface which are employed for working the ball raceways.
The wobble extrusion die is then set into a wobble motion whereby it is rolled over the surfaces of the preliminary workpiece which are to be formed, in a plurality of circular orbits. The wobble point of this movement is thereby just below the underside of the preliminary workpiece. During the wobble extrusion in each case only a small region of the ball raceways to be shaped is shaped. When the desired shapings are attained with the preliminary workpiece, the wobble procedure is ended and the wobble extrusion die is again removed. Advantageous with this known method is that a one-piece wobble die can be employed which can be manufactured more economically than a multi-piece segment die and which ensures a high precision in the manufacture of joint outer parts.
The object of the invention is to employ the wobble procedure with a one-piece wobble extrusion die, known for the manufacture of Rzeppa constant velocity joints, also for the manufacture of cross groove constant velocity joints.
The wobble extrusion die in accordance with the invention hasxe2x80x94in a projection directed perpendicular to its axisxe2x80x94straight line projection edges and is particularly simply and economically manufacturable.